1. Field of the Invention
The present invention relates to a liquid cooled type rotating electrical machine with an improved circulating path for liquid coolant.
2. Description of the Related Art
Heretofore, as a liquid cooled type rotating electrical machine where cooling liquid is introduced into a housing, and a stator is cooled by the cooling liquid, there are known for example, the rotating electrical machines of Japanese Examined Patent Application, Second Publication No. Sho. 60-36696, and U.S. Pat. No. 4709180.
With the former rotating electrical machine, the stator body is cooled by the cooling liquid, while with the latter rotating electrical machine, the cooling liquid is circulated inside the rotor for cooling.
However, when an Nd-Fe-B magnet is used for the rotor, the generating efficiency is increased accompanying the high magnetic flux due to the large energy product. With an increase in temperature of the magnet itself however the magnetic force is reduced, and hence the generating efficiency drops.
On the other hand, in the case where electricity generation is carried out at high rotational speeds exceeding several ten thousand rpm, generating in the stator copper losses and eddy current losses produced in the winding section, and core losses produced in the core section, these losses are all converted to heat so that the stator comes into a high temperature condition.
Therefore, in order to realize high efficiency power generation, it becomes important to efficiently cool the inner periphery of the stator close to the rotor, so that the characteristics of the magnet are not impaired.
The present invention takes into consideration the above situation with the object of efficiently cooling the stator.
In order to achieve the above object, the present invention adopts the following devices.
That is, according to the present invention, a rotating electrical machine is provided, in which a cylindrical shape stator is accommodated inside a housing, a rotor is rotatably supported on an inner peripheral side of the stator, and a cooling circuit for introduces cooling liquid (oil with this embodiment) to inside the housing for cooling an inner periphery and an outer periphery of the stator in that order.
With this construction, low temperature cooling liquid which has just been introduced to the housing, and has not yet been supplied for cooling the heat source, is promptly circulated to the inner peripheral side of the stator which requires much more cooling than the outer peripheral side of the sator.
Therefore, it becomes possible to efficiently cool the stator using the low temperature cooling liquid. Hence the temperature rise of the overall rotating electrical machine is suppressed.
Furthermore, with the above construction, in the case where there is provided a non return device (a cover plate with this embodiment) for preventing back flow of the cooling liquid introduced inside the housing, to an outer peripheral side of the stator, the cooling liquid introduced to inside the housing is reliably conducted to the inner peripheral side of the stator close to the rotor before to being conducted to the outer peripheral side of the stator far from the rotor.
Furthermore, with either of the above constructions, in the case where the cooling liquid is also used for lubrication of bearings supporting the rotor, the circuit necessary for lubrication and cooling can be simplified.
Moreover, with any of the above constructions, with a stator winding where heat conducting particles (BN particles with this embodiment) are filled into the stator winding, and moreover when a resin such as varnish is also impregnated, into the stator winding this is impregnated with the heat conducting particles mixed into the impregnating resin and is then hardened, then the thermal conductivity of the impregnated resin portion is improved. Hence, heat dissipation of the stator winding is enhanced and the cooling efficiency is further improved.